Use of face masks did not impact COVID-19 incidence among 10–12-year-olds in Finland

Aapo JuutinenEmmi SarvikiviPäivi Laukkanen-NevalaOtto Helve


In fall 2021 in Finland, the recommendation to use face masks in schools for pupils ages 12 years and above was in place nationwide. Some cities recommended face masks for younger pupils as well. Our aim was to compare COVID-19 incidence among 10–12-year-olds between cities with different recommendations on the use of face masks in schools. COVID-19 case numbers were obtained from the National Infectious Disease Registry (NIDR) of the Finnish Institute for Health and Welfare, where clinical microbiology laboratories report all positive SARS-CoV-2 tests with unique identifiers in a timely manner, including information such as date of birth, gender, and place of residence. The NIDR is linked to the population data registry, enabling calculation of incidences. We compared the differences in trends of 14-day incidences between Helsinki and Turku among 10–12-year-olds, and for comparison, also among ages 7–9 and 30–49 by using joinpoint regression. According to our analysis, no additional effect seemed to be gained from this, based on comparisons between the cities and between the age groups of the unvaccinated children (10–12 years versus 7–9 years).

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study did not receive any funding.

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.


The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Director of the Department for Health Security of Finnish Institute for Health and Welfare is the competent authority for assessing whether research requires institutional ethical review or if the Finnish communicable diseases law (Tartuntatautilaki 1227/2016) and the law on the duties of the Finnish institute for Health (Laki Terveyden ja hyvinvoinnin laitoksesta 668/2008) and Welfare allows the implementation of the research without seeking further ethical review. Based on his decision this research did not require further ethical review before implementation as its aim was to monitor the effectiveness of specific mitigation measures based on surveillance data (Tartuntatautilaki 1227/2016). The official document including the statement with signature, can be provided if necessary.

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Paper in collection COVID-19 SARS-CoV-2 preprints from medRxiv and bioRxiv